Light-weight aggregate



Patented Get. 6, 1925.

UNITEDLSTATES PATENT OFFICE.

' No Drawing.

To all whom it may concern: I

Be it known that I, GEORGE A. WALKLEY, a citizen of the United States of America,

residing at Westfield, in the county of.

6 Hampden and State of Massachusetts, have invented certain new and useful Improvements in. Light-Weight Aggregates, of which the following is a specification. This invention relates to a process for 10 making a light weight aggregate suitable for constructlon purposes. While the process is independent Ofl the use to which the product is put, it may be pointed out that. the product is particularly advantageous as an aggregate in the making'of concrete.

Broadly. considered, the invention con' sists in making a plastic mixture of a suit able brick-forming material, such as .clay, with a combustible material, such as coal dust, saw dust or the like, and subsequently burning the mixture in a manner similar to brick burning, but more rapidly and with.

sufiicient heat'to harden the material into a strong compact form of porous density, but

not with high enough heat to drawthe material together into a vitrified solid mass.

In a general way, the invention is carried out as follows; the clay and combustible v material are thoroughly ground together 3 with water until the mass is of the desired plasticity, in a manner analogous to that employed in the art of brick making, as in a pug mill. The plastic mass is'then preferably molded into blocks which are partialv 1y dried to a degree suflicient to permit stacking; the blocks are then stacked into a kiln and the latter fired; characterized in that the fire is forced rapidly to supply an intensedieat and maintained continuously so 40 that the emission of the water-smoke is uninterruptedk o The process is characterized by its relative rapidity over the. usual methods of burning brick. The usual complete dryin'g ofthe bricks in the present process is, in

. practical efi'ect, omitted as only partial drying of'relatively short duration is employed and for'the purpose specified. The actual enoaen a. WALKLEY, orwasrrmnn, MASSACHUSETTS LIGHT-WEIGHT AGGREGATE.

Application filed January 23', 1920. Serial- No. 853,638.

burning process is also comparatively rapid, I the fire being rushed from the start to the end of this step of the process. 1

Other features of the mvention'will apv pear in thefollowing more detailed description.

. The preliminary step of the process consists in the thorough mixture of the materials to be burned. Broadly, the major element of this mixture is a Suitable clay, and various clays may be used. It has been found that a particular kind of clay, te(:h so nically known as soft shale, is especially adapted for this process, but the processv is not confined to the use of this specific kind of clay although it is at present preferred.

For the combustible element of the mixture, various materials may be em loyed, but coal is particularly suitable,- w en in finely subdivided form, as it readily lends itself to admixture with the clay and may be distributed therethrough with substantial uniformity. Preferably, coal dust, eitherof anthracite or bituminous coal, may be used although a mixture of anthracite with a long flame bituminous coal has proved in practice particularly satisfactory.

The proportions of the clay and combustible elements may be varied within wide limits, as desired, to efi'ect varyin degrees of porosity and thus control the ensity of the product. Exact proportions -of the two main ingredients are, therefore, not essential to successin'practicing the-process. In actual praotice, these two ingredients are seldom measured with an degree of, accuracy, but it maybestated that, with the articular combustible and the particular 'nd of clay mentioned, a suitable light weight aggregate is obtained by a mixtureof nine partsfof clay .to one part of coal'dust.

Preferably, although not necessarily, there is added to the main elements described a suitable flux, such as a mixtureof sulphur andborax for example. Generally, this'isapplied asa sprinkling to each batch as it is made u For example, a batch weighing approximately 2000 pounds will consist'of about 1800 pounds of clay,

200 pounds of coal dust and a handful of sulphur and a handful of borax.

The mixing of the constituents described may be accomplished in any suitable manner, They may, however, be mixed to ad vantage in a manner analogous to that employed in the art of brick making. as by placing the constituents in a pug mill which operates to thoroughly grind and mix the materials. At this time, water is added to the mixture until it is rendered of sutficient plasticity. These steps are substantially like those usually employed in brick making.

The mass, having been brought to the desired degree of plasticity, is then preferably molded into blocks or bricks, preliminary to the step of burning. The purpose of this step is merely to facilitate burning. That is, the question of the final size and shape of the burned productis not ordinarily 'of particular importance, but it is convenient to mold the mass into bricks so that they can readily be stacked into kiln form for the step of burning.

Before the bricks. are burned, they. are partially dried, as distinguished from complete drying customary in the preparation of ordinary bricks for burning in a kiln. The purpose of this step is merely to dry the bricks to a degree sufficient to permit them to be stacked into a kiln.

The burning of the kiln is generally analogous to the burning of a kiln of ordinary bricks with the exception that the firing throughout is more rapid than in ordinary brick burning. The fuel may be chosen as desired except that a fuel which will quick- 1y yield an intense heat and lend itself to forcing is preferable. Contrasted with orc inary brick burning, the fire is forced throughout to a relatively intense heat, and followed up to prevent diminution of the heat. The purpose of firing in this manner is to quickly cause the generation of gases in the plastic bricks and to continue the generation and emission of gases from the bricks without interruption until exhaustion of the sources of gas. The degree of heat employed is gauged to effect the results just named. Generally, the bricks are heated from 17O0 to 1900 Fahr. The gases, which are commonly termed water smoke, are forced from the bricks in a continuous manner by forcing the fires for this purpose. The characteristic feature of the step of burning is the rapid and intense initial heat and the forcing and following'up of the fire to'secure complete emission of the ases. The time of rapid and intense firing 1s gauged by watching the emission of the water-smoke. For example, at the start of the step of burning the operator forces his fire to higher and higher temperatures until he observes the emission of the water-smoke.

He then continues forcing the fire :a. a never allows it to slacken until he is assured from the cessation of water-smoke, even under intense heat, that the exhaustion of the sources of gas is complete. After the emission of water-smoke has ceased, the burning may be continued for a short time, if desired, but care should be taken not to burn the bricks into a vitrified solid mass. A higher degree of heat than 2000 Fahr. or a continued heating after the Water-smoke has been expelled from the brick will generally cause vitrification of the brick into a solid dense mass which it is desired to avoid in this process.

By carrying out the present process as described, it will be found that the brick is burned to a strong tough body of porous density so as to be extremely light as compared to ordinary brick. The bricks formed by the present process will generally be found to be swelled to alarger size than the original molded blocks and with rounded or bulging sides. In other words, they have the appearance of being blown up like raised and baked bread.

The bricks when thus finished may be used as ordinary bricks, but may also be broken up into pieces of the desired size to serve as an aggregate of concrete. The advantages of a strong light weight aggregate for such purpose is apparent.

What I claim is- 1. The process of making a light weight aggregate, which consists in mixing clay and finely divided fuel into a plastic mass, forming the mass into separate units, partially drying such units sufficiently for stacking into a kiln, stacking the units into a kiln, and in then rapidly firing the kiln with an intense heat.

2. The process of making a light weight aggregate which consists in mixing clay and finely divided fuel into a plastic mass, forming the mass into separate units, partially drying such units suificientl and in then rapidly firing the kiln to a temperature approximately between 1700 Fahr. and 1900 Fahr.

3. The process of making a light weight aggregate, which consists in mixing clay and finely divided fuel into a plastic mass, forming the mass into separate units, partially drying such units sufiiciently for stacking into a kiln, stacking the units into a kiln, in then rapidly firing the kiln to a temperature approximately between 1700 Fahr. and 1900 Fahn, and continuing'said firing of the kiln until all apparent watersmoke has been driven off.

4. The process of making light weight aggregate, which consists in mixing clay and finely divided coal into a plastic mass in approximate proportions of nine parts for stackinginto a kiln, stacking the units into a kiln,

of clay and one part of coal and subjecting the same to a temperature of approximatel between 1700 and 1900 Fahr. for a. su ficient length of time to harden the same into a porous, burned clay product, but not sufiicient to vitrify the same into a solid non-porous structure.

5. 'IIhe process of making light weight aggregate, which consists in mixing clay 1 and finelydiirided coal into a. plastic mass in approximate proportions of nine parts of clay and one part of coa1,'together with traces of sulphur and borax added as a flux, and subjecting the same to a temperature of approximately between 1700 and 1900 Fahrt for a sufiicient length of time to harden the same into a porous, burned clay product, but not s uflicient to vitrify the same into a solid non-porous structure.-

GEORGE A/WALKLEY. 

